Directive-projecting system of electric waves



Jan. 28, 1930. w H. YAGI 1,745,342

DIRECTIVE PROJECTING SYSTEM OF ELECTRIC WAVES F'i'led Sept. 3, 1926 Fig.2

Z r I Irm er-mtob I Hidetsugu Yagi Hi5 Attohey Patented Jan. 28, 1930 a UNITED STATES PATENT OFFICE irrnnrsnetr YAGI, or SENDAI, JAPAN, ASSIGNOR T RADIO coRroRATIoN OF AMERICA OF NEW YORK, N. Y., A CORPORATION OF DELAWARE DIRECTIVE-PROJECTING SYSTEM OF ELECTRIC WAVES Application filed September 3, 1926, Serial No. 133,456, and in Japan January 20, 1926.

The present invention relatesito a directive wireless system or more particularly to an [antenna system comprising a plurality of vertical conductors or antennae having special lengths or natural frequencies located in a 'definite'relation with a main vertical antenna, and has for its object the provision of simple and effective means for transmitting or receiving wireless signal or electric wave energy in a definiteisdlrection with utmost sharpness and intensity.

" *F or a consideration of what I believe to be novel and my invention, attention is directed I tothe accompanying description and claims appended thereto. i

In the drawing, Fig. 1 is a diagrammatic view of arrangement of vertical antennae embodying my invention taken for explanation of-its priciple; Fig. 2 is a plan viewof an antenna" system embodying my invention; and Fig. 3' is a similar view representing another embodiment of my invention.

I have found out as the result of numerous experiments that if a vertical conductor 01' antenna is located at asuitable distance from a vertical antenna which effects wireless communication said conductor will present a pcculiar effect to the characteristics of the main antenna by the suitable selection of the natural frequency and position of said conductor and also that if-tlie natural frequency is taken .equal to or lower than the wave frequency then the conductor will act as a Wave reflector, that is,.it reflectsthe electric wave either issued from the main antenna or arriving to it from other wireless station, while on the contrary if the natural frequency of the conductor-is selected higher than wave frequenin the direction of the director.

cv it acts as a wave director. that is, the electi'ic wave energy is absorbed in the conductor and then re-radiated ortransmitted further I The present invention relates to a novel system for directing 'electro-inagnetic wave energy with conductors of the above nature located in 455, filed eptember 3,1926.

Ndw reference is had to the accompanying drawing for a better understanding of my invention. Referring to Fig. 1, 1 is a main vertical antenna suitably connected or coupled to a wireless receiving or sending means 2. At suitable distances Z and L from the main antenna 1 are vertical conductors 3 and 4 respectively, the antenna 1 being insulated from. the earth and other objects. The conductor 3 has natural frequency equal to or lower than the frequency of sending or receiving eleetro-magnetic wave, while the conductor 4 is made to have a suitable higher natural frequency than the frequency of said wave. The distances Z and L of these conductors from the main antenna should of course be selected properly in order to obtain the highest possible efficiency as hereinafter described. Now assuming that the electric wave energy is radiated from the main antenna 1 it will be evident from the foregoing that the conductor 3 reflects the electric wave, while the conductor 4 transmits the wave. Accordingly in the arrangement shown in Fig. 1, the electric wave will be mainly projected in the direction of the conductor 4 and it is reflected in the direction of conductor3. It is not necessary in all cases to arrange these conductors 3 and 4 in a straight line together with the antenna 1, but they may be located in various relation as will be clear hereafter.

In a system of antenna embodying my invention as shown in Fig. 2 the main antenna 1 is erected substantially in a vertical position and electrically insulated from the earth and its length is so designed as to oscillate at one-half wave length. A plurality of vertical conductors 2, 3, 3, 4 and 4 are arranged at suitable distances respectively from the main'antenna 1 and electrically insulated from the earth and from each other, so as to constitute a wave reflecting system. These conductors may be of metallic wires or rods which are longer than one-half wave length,

arranged substantially parallel with the main antenna 1. Now the electrical charactercal phase angle behind the induced electromotive force.

I have arranged one or more conductors such as 5. 5, 5 and 5 in front of the main antenna 1 with regard to the above mentioned conductors which being in rear constitute said reflecting set. These conductors 5, 5, 5 and 5 may be metallic wires or rods and are electrically insulated from the earth, situated in substantially vertical position along a straight line (or suitable curved line) including the antenna 1, and are shorter than one-half wave length, such, for instance, as 0.8 to 0.95 of one-half wave length. The current induced in these vertically arranged conductors is in leading phase'as against the.

phase of the electro-motive force; These series of conductors 5, 5 etc. constitute a wave-canal or wave-duct, each of which conductors being called a wave-director.

According to this embodiment of my invention as arranged as shown in Fig. 2, a plurality of conductors 2, 3, 3, 4 and 4" arranged around the main antenna 1 constituting a reflecting unit are energized with lagging current if the antenna 1 is energized for sending or receiving signals, and thereby effects the reflecting or collecting action of electric wave. Meanwhile the leading current is induced in each of the conductors 5, 5 etc. belonging to the wave transmitting system and tends to guide or project the electric wave along a line which joins these conductors. Thus two sets or groups of conductors having different characteristics with regard to the incident electric wave will ointly act to effectively assist the directional receiving or sending of wireless signals or wireless wave energy. I

In Fig. 3 I have shown a special arrangement of the conductors, which were found out experimentally to give the most effective operation according to my invention. I have settled in this case the relative position of each conductor constituting a member of refleeting and transmitting units with regard to the antenna 1 as follows: The conductor 2 of the reflecting unit is located at a distance of one-quarter wave length behind the main antenna 1, and the conductors 3 and 3 are situated respectively at the left and right hand of the straight line joining the antenna 1 and conductor 2 at a distance of one-half wave length, so as to form a triangle with the points 2, 3 and 3 at the apices. The above arrangement. of 2, 3 and 3 constitutes a trigonal reflector. Each of the conductors 5,5, 5", 5', etc. constituting awave-director is located at a distance more than one-quarter wave length from the antenna 1 and from each other along a straight line (or a suitable curve) including the antenna 1 and conductor'2. Though I may use one or more of the conductors constituting the wave-director, preferably I make use of many. In the arrangement shown, I have added two more conductors 4 and 4 at middle points of two sides 2, 3 and 2', 3 of the triangle. These conductors have similar characteristics to that of each conductor in the reflecting set These additional conductors 4 and 4, though they are not effective for reflecting action, present an important service in shielding the antenna 1 against electric waves coming from unexpected direction, thereby preventing t'hc confusion of signalling and rendering the action of the reflector far more effective.

In short, myinvention comprises essentiailly a vertical main antenna, awave-reflecting set consisting of one or more conductors each having natural frequency equal to or lower than the wave frequency and erected behind or around the main antennasubstanmain antenna, my invention makes it possible to project the sharpest beam of electric wave ever produced for directive wireless communication.

The adjustment of the natural frequency is effected by altering the length of the conductoror by the employment of adjustable inductances or variable condensers.

Since it is apparent that many modifications may be made of the arrangements of my invention shown and described herein without departing from the scope of the invention as set forth in the appended claims, I do not wish to be limited by the particular arrangements only disclosed herein.

What I claim as new and desire to secure by Letters Patent'of the United States, is:

1. In a system for projecting or receiving electric waves comprising a vertical main antenna, a wave reflector consisting of a vertical conductor having natural frequency equal to or lower than the wave frequency arranged on one side and at-a suitable distance from said main antenna, and a wave directive reflector consisting of a vertical conductor having natural frequency higher than the wave frequency'located on the other side and at a suitable distance from said main antenna.

2. In a system for projecting or receivlng electric waves comprising a vertlcal main an tenna, a wave reflecting set consisting of a? plurality of vertical conductors having natural frequency equal to or lower than the wave frequency arranged at a suitable distance from said main. antenna and in its rear and sides and a wave directive set consisting of a plurality of vertical conductors having natural frequency higher than the wave freconductors and located at mi quency situated in front of the main antenna along substantially a straight line.

3. In a system for projecting or receiving electric waves comprising a vertical main antenna, a trigonal Wave reflector consisting of a vertical conductor located at a distance of one-quarter wave length behind said main antenna and two vertical conductors each located on the right and the left hand sides of said main antenna and at a distance of onehalf wave length from said antenna, all'of said conductors having natural frequency equal to or lower than the wave frequency, and a wave-directive set consisting of a number of vertical conductors arranged in front of and at a distance more than one-quarter wave length from said main antenna and then successively spaced from each other along substantially a straight line, the conductors having natural frequency higher than the wave frequency. I

4;. In asystem for projecting or receiving electric waves comprising a vertical main antenna, a series of vertical conductors in front of and apart from said main antenna more than one-quarter wave length and successively spaced along a straight line including said antenna, said conductors having natural frequency higher than the wave frequency, a vertical'conductor having natural requency lower than the wave frequency located at a distance of one-quarter ware length v behind said main antenna, two conductors each similar to the former situated on a perpendicular to the line passing through said main antenna and other conductors and located on each side of the line at a distance of one-half wavelength from the main antenna, and two more conductors similar to the former situated on a line joinin three former ddle points between said three conductors, all of said conductors being electrically insulated from each other.

5. In a wireless system embodying a vertical main antenna, a wave reflecting set which includes a Vertical conductor insulated from earth, its length being equal to or exceeding more than one-half wave length, the same being positioned to one side of and at a a suitable distance from the antenna, and a wave directiveset consisting'of a vertical conductor insulated from earth and having length less than one-half wave length located on the other side and at a suitable distance wave reflector consisting of a conductor having natural frequency equal to or lower than 1 the wave frequency arranged on one side and at a suitable distance from said main antenna,

I and a wave directive reflector consisting of a conductor having natural frequency higher than the wave frequency located on the other side and at a suitable distance from said main antenna.

7. In a system for projecting or receiving electric waves comprising a linear main antenna, a wave reflector consisting of a linear conductor having natural frequency equal to or lower than the wave frequency arranged on one side and at a suitable distance from said main antenna, and a wave directive refiector consisting of a linear conductor having natural frequency higher than the wave frequency located on the other side and at a suitable distance from said main antenna.

8. In a wireless system embodying a linear main antenna, a wave reflecting set which includes a linear conductor insulated from the earth, its length being e ual to or exceeding more than one-half wave ength, the same being positioned to one side of and at a suitable distance from the antenna, and a wave director set including a linear conductor insulated from earth and having length less than onehalf wave length located on the other side and at a suitable distance from the main antenna.

9. An antenna system comprising a main antenna, another antenna behind the main antenna, tuned to a frequency lower than a desired signal frequency, for wave reflection; and, another antenna in front of the main antenna tuned to a frequency hi her than the desired signalling frequency, or wave di- 

